Integrated PVD system for aluminum hole filling using ionized metal adhesion layer

ABSTRACT

A hole filling process for an integrated circuit in which two wiring levels in the integrated circuit are connected by a narrow hole, especially where the underlying level is silicon. First, a physical vapor deposition (PVD) process fills a barrier tri-layer into the hole. The barrier tri-layer includes sequential layers of Ti, TiN, and graded TiN x , grown under conditions of a high-density plasma. Thereafter, a first aluminum layer is PVD deposited under conditions of a high-density plasma. A filling aluminum layer is then deposited by standard PVD techniques.

RELATED APPLICATIONS

This application is a division of U.S. patent application, Ser. No.08/679,547, filed Jul. 12, 1996, now abandoned which is a continuationin part of U.S. patent application, Ser. No. 08/628,835, filed Apr. 5,1996, which is a continuation in part of U.S. patent application, Ser.No. 08/511,825, filed Aug. 7,1995, now issued as U.S. Pat. No.5,962,923. application Ser. No. 08/628,835 is now abandoned but has beenrefiled as U.S. patent application, Ser. No. 08/977,007, file Nov. 24,1997, now issued as U.S. Pat. No. 6,045,666.

FIELD OF THE INVENTION

The invention relates generally to semiconductor integrated circuits. Inparticular, the invention relates to a barrier layer formed between ametal and a semiconductor, and the covering of the barrier layer with aconductor.

BACKGROUND OF THE INVENTION

Modem semiconductor integrated circuits usually involve multiple layersseparated by dielectric (insulating) layers, such as of silicon dioxideor silica, often referred to simply as an oxide layer, although othermaterials are being considered for the dielectric. The layers areelectrically interconnected by holes penetrating the intervening oxidelayer which contact some underlying conductive feature. After the holesare etched, they are filled with a metal, such as aluminum, toelectrically connect the bottom layer with the top layer. The genericstructure is referred to as a plug. If the underlying layer is siliconor polysilicon, the plug is a contact. If the underlying layer is ametal, the plug is a via.

Plugs have presented an increasingly difficult problem as integratedcircuits are formed with an increasing density of circuit elementsbecause the feature sizes have continued to shrink. The thickness of theoxide layer seems to be constrained to the neighborhood of 1 μm, whilethe diameter of the plug is being reduced from the neighborhood of 0.25μm or 0.35 μm to 0.18 μm and below. As a result, the aspect ratios ofthe plugs, that is, the ratio of their depth to their minimum lateraldimension, is being pushed to 5:1 and above.

Filling such a hole with a metal presents two major difficulties.

The first difficulty is filling such a hole without forming an includedvoid, at least with a filling process that is fast enough to beeconomical and at a low enough temperature that doesn't degradepreviously formed layers. Any included void decreases the conductivitythrough the plug and introduces a substantial reliability problem.Chemical vapor deposition (CVD) is well known to be capable of fillingsuch narrow holes with a metal, but CVD is considered to be too slow fora complete filling process. Physical vapor deposition (PVD),alternatively called sputtering, is the preferred filling processbecause of its fast deposition rates. However, PVD does not inherentlyconformally coat a deep and narrow hole. A fundamental approach forapplying PVD to deep holes is to sputter the metal on a hot substrate sothat the deposited material naturally flows into the narrow and deepfeature. This process is typically referred to as reflow. However,high-temperature reflow results in a high thermal budget, and in generalthe thermal budget needs to be minimized for complex integratedcircuits. Further, even at high temperatures, the metal does not alwayseasily flow into a very narrow aperture.

The second difficulty is that an aluminum contact is not reallycompatible with the underlying semiconductive silicon. At moderatelyhigh temperatures, such as those required for the reflow of aluminuminto the narrow hole, aluminum tends to diffuse into the silicon and toseverely degrade its semiconductive characteristics. Accordingly, adiffusion barrier needs to be placed between the aluminum and theunderlying silicon.

These problems are well known and have been addressed by Xu et al. inU.S. patent application, Ser. No. 08/628,835, filed Apr. 5, 1996,incorporated herein by reference in its entirety, which is acontinuation in part of U.S. patent application, Ser. No. 08/511,825,filed Aug. 7, 1995 now U.S. Pat. No. 5,962,923.

As shown in the cross-sectional view of FIG. 1, a contact hole 10 havingan aspect ratio defined by its depth 12 and its width 14 is etchedthrough a dielectric layer 16 to an underlying substrate 18, which inthe more difficult situation includes a surface layer of silicon. In thehole filling process, the contact hole 10 is conformally coated with atitanium (Ti) layer 20, a titanium nitride (TiN) layer 22, and a graded(TIN_(x)) layer 24, that is, the graded layer 24 begins at its bottom asTiN but its top portion is nearly pure Ti. These three layers form atri-layer barrier 26, which provides both the conformality and theadhesion to the underlying layers, as well as sufficient wetting for theafter deposited aluminum. A Ti layer 20, after siliciding at thesufficiently high annealing temperature, forms a good ohmic contact withthe underlying silicon substrate 18. Thereafter, a metal layer 28 issputter deposited into the hole 10 so as to fill it without voids. Thatis, the tri-layer barrier 26 sufficiently wets to the after filledaluminum that it readily flows into the hole 10 at a moderatetemperature while the tri-layer barrier 26 nonetheless provide asufficient diffusion barrier between the aluminum 28 and the underlyingsilicon 18.

According to Xu et al., the wetting quality of the three layers 20, 22,24 is enhanced by depositing them in a high-density PVD reactor. On theother hand, they recommend that the aluminum layer 28 be sputterdeposited in a conventional PVD chamber with a low plasma density. Inparticular, they recommend that the aluminum layer 28 be deposited astwo layers in an improved two-step cold/warm version of a conventionalsputtering process. In the first cold step, a seed layer 30 of aluminumis sputter deposited at a substrate temperature below 200° C. so as toconformally coat the underlying barrier tri-layer 26 with a fairlyuniform aluminum layer. In the second warm step, a filling layer 32 ofaluminum is sputter deposited at higher temperatures so as to reflow andfill the contact hole 10. An advantage of the tri-layer barrier 26 grownby ionized metal plating (IMP) is that the warm Al filling layer 32 canbe filled at temperatures below 400° C., even as low as 350° C.according to the reported data. The warm layer 32 can be deposited at afairly high rate so as to improve the system throughput. Because the twoaluminum layers 30, 32 differ primarily in their different depositiontemperatures, they are likely deposited within a single conventional PVDchamber capable only of developing a low-density plasma. Also, the twodeposition can be performed continuously, with the temperature beingramped up during the deposition. As a result, the two Al layers 30, 32have no clear boundary between them.

In the context of contact hole filling, a high-density plasma is definedin one sense as one substantially filling the entire volume it is in andhaving an average ion density of greater than 10¹¹ cm⁻³ in the principalpart of the plasma. The conventional plasma-enhanced PVD reactorproduces a plasma of significantly lower ion density. Althoughhigh-density plasmas are available in a number of different types ofreactors, they are preferably obtained in an inductively coupled plasmareactor, such as the type shown in schematical cross section in FIG. 2.For reasons to be described shortly, this is referred to an ionizedmetal plasma or plating (IMP) reactor.

As shown in this figure, which is meant only to be schematical, a vacuumchamber 40 is defined principally by a chamber wall 42 and a targetbacking plate 44. A PVD target 46 is attached to the target backingplate 44 and has a composition comprising at least part of the materialbeing sputter deposited. For the deposition of both titanium (Ti) andtitanium nitride (TiN), the target 46 is made of titanium. A substrate48 being sputter deposited with a layer of a PVD film is supported on apedestal electrode 50 in opposition to the target 46. Processing gas issupplied to the chamber 40 from gas sources 52, 54 as metered byrespective mass flow controllers 56, 58, and a vacuum pump system 60maintains the chamber 40 at the desired low pressure.

An inductive coil 62 is wrapped around the space between the target 46and the pedestal 50. Three independent power supplies are used in thistype of inductively coupled sputtering chamber. A DC power supply 64negatively biases the target 46 with respect to the pedestal 50. An RFpower source 66 supplies electrical power in the megahertz range to theinductive coil 62. The DC voltage applied between the target 46 and thesubstrate 48 causes the processing gas supplied to the chamber todischarge and form a plasma. The RF coil power inductively coupled intothe chamber 40 by the coil 62 increases the density of the plasma, thatis, increases the density of ionized particles. Magnets 68 disposedbehind the target 46 significantly increase the density of the plasmaadjacent to the target 46 in order to increase the sputteringefficiency. Another RF power source 70 applies electrical power in thefrequency range of 100 kHz to a few megahertz to the pedestal 50 inorder to bias it with respect to the plasma.

Argon from the gas source 54 is the principal sputtering gas. It ionizesin the plasma, and its positively charged ions are attracted to thenegatively biased target 46 with enough energy that the ions sputterparticles from the target 46, that is, target atoms or multi-atomparticles are dislodged from the target. The sputtered particles travelprimarily along ballistic paths, and some of them strike the substrate48 to deposit upon the substrate as a film of the target material. Ifthe target 46 is titanium or a titanium alloy and assuming no furtherreactions, a titanium film is thus sputter deposited, or in the case ofan aluminum target, an aluminum film is formed.

For the sputter deposition of TiN in a process called reactivesputtering, gaseous nitrogen is also supplied into the chamber 40 fromthe gas source 52 along with the argon. The nitrogen chemically reactswith the surface layer of titanium being deposited on the substrate toform titanium nitride.

As Xu et al. describe in the cited patent application, a high-densityplasma, primarily caused by the high amount of coil power applied to thechamber 40, increases the fraction of the sputter species that becomeionized as they traverse the plasma, hence the term ionized metalplating. The wafer bias power applied to the pedestal 50 causes thepedestal 50 to become DC biased with respect to the plasma, the voltagedrop occurring in the plasma sheath adjacent to the substrate 48. Thus,the bias power provides a tool to control the energy and directionalityof the sputter species striking the substrate 48.

Xu et al. disclose that the Ti/TiN/TiN_(x) barrier tri-layer 26 shouldbe deposited in an ionized metal process plating (IMP) process in whichthe various power levels are set to produce a high-density plasma. Theyobserve that an IMP barrier tri-layer 26 as shown in FIG. 1, whendeposited in the contact hole 10, promotes the reflow of aluminum intothe contact hole 10 when the aluminum is subsequently deposited in aconventional PVD reactor, that is, one not using inductively coupled RFpower and not producing a high-density plasma. This superior reflow isbelieved to require two characteristics in a narrow aperture. Thebarrier layer needs to adhere well to the underlying SiO₂ or Si so as toform a continuous, very thin film. The aluminum needs to wet well to thebarrier layer so that it flows over the barrier layer at relatively lowtemperatures.

Although the TiN IMP barrier tri-layer offers significant advantages inpromoting reflow of subsequently deposited conventional PVD aluminum, asprocessing requirements become even more demanding, further improvementof reflow into narrow apertures is desired.

SUMMARY OF THE INVENTION

The invention can be summarized as a method of filling a narrow hole andthe structure resultant therefrom in which the hole is first filled witha barrier layer comprising one or more layers of TiN or other refractorymetal materials. Thereafter, a non-refractory metal, such as aluminum iscoated into the hole with an ionized metal process (IMP), that is, inthe presence of a high-density plasma. Thereafter, the remainder of thehole is filled with a standard PVD process involving a low-densityplasma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematical cross-sectional view of a known type of contactin an integrated circuit.

FIG. 2 is a schematical side illustration of a ionized metal process(IMP) reactor for physical vapor deposition (PVD).

FIG. 3 is a schematical cross-sectional view of a contact in anintegrated circuit according to the invention.

FIG. 4 is a flow diagram of an aluminum hole filling processincorporating the invention.

FIG. 5 is a scanning electron micrograph (SEM) of a contact of theinvention.

FIG. 6 is a SEM of a contact of the prior art showing the formation ofvoids.

FIG. 7 is a schematical plan view of an integrated processing toolincorporating various reaction chambers usable with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A contact formed according to the invention is illustrated in crosssection in FIG. 3. The contact is formed in the contact hole 10 etchedin the oxide layer 16 overlying the silicon surface of the substrate 18.Just as in Xu et al.'s structure illustrated in FIG. 1, an IMP barriertri-layer 26 is deposited into the contact hole 10. The barriertri-layer includes a Ti layer 20, a TiN layer 22, and a graded TiN_(x)layer 24, all sputtered in a high-density plasma by an ionized metalplating (IMP) process.

According to the invention, an IMP aluminum layer 70 is sputterdeposited over the barrier tri-layer 26 in an IMP process, that is, in ahigh-density plasma, for example as practiced in the reactor of FIG. 2.A standard aluminum layer 72 is sputter deposited over the IMP aluminumlayer 70, preferably by a conventional PVD process utilizing alow-density plasma. The IMP aluminum layer 70 is easily conformallycoated into the contact hole 10 and forms a seed layer for the afterdeposited aluminum filler layer 72. Advantageously, the IMP aluminumlayer 70 can be deposited at near to room temperature, and the aluminumfiller layer 72 can effectively fill the contact hole 10 at relativelylow deposition temperatures. That is, the total process has a lowthermal budget. Nonetheless, the contact hole is effectively filled andplanarized.

The complete processing sequence for a preferred processing embodimentof the invention is shown by the flow diagram of FIG. 4. In step 80, acontact hole is etched through the overlying oxide layer to theunderlying substrate having at least a silicon surface in the vicinityof the contact hole. After some cleaning steps described in the examplebelow, in step 82, an IMP PVD chamber sputter deposits a titanium layerinto the hole. In step 84, the titanium layer is annealed so as besilicided to the underlying silicon. In step 86, an IMP PVD chamberreactively sputters a layer of TiN over the titanium layer in thecontact hole by additionally admitting nitrogen into the reactionchamber. In step 88, the PVD chamber sputter deposits the graded TiN_(x)layer onto the TiN layer. This is most typically accomplished by cuttingoff the supply of nitrogen from the previous step 86, and the residualnitrogen in the chamber or embedded in the Ti target is graduallydepleted until a pure Ti layer is being deposited. In step 90, the waferis transferred to another IMP PVD chamber in which a layer of aluminumis deposited by IMP. In step 92, the wafer is transferred to a standardPVD chamber, which deposits an aluminum filling layer in a standard warmprocess.

EXAMPLE

Contact holes were etched through a dielectric layer of SiO₂ having athickness of 1.2 μm. The contact holes had diameters of 0.35 μm. Thus,the contact hole had an aspect ratio of 3.5:1. Prior to the PVDdeposition, the etched wafer was subjected to one minute of PVDdegassing and a pre-cleaning which removed an equivalent of 25 nm ofoxide.

The wafer was then transferred into a first IMP chamber, such as thatillustrated in FIG. 2, for deposition of the barrier tri-layer. Thetitanium target was DC biased at 6 kW, the coil was RF biased at 1.5 kW,and the pedestal during the titanium process was sufficiently RF biasedto create about a −50V DC bias with respect to the plasma. The tri-layerwas then formed having a titanium thickness of 20 nm, a TiN thickness of80 nm, and a TiN_(x) thickness of about 10 nm resulting from a 5 sectitanium sputter after cutoff of the nitrogen.

The wafer was then transferred to another IMP chamber having an aluminumtarget. The biasing conditions were the same except that no bias wasapplied to the pedestal. (The presence of bias on the pedestal wasdemonstrated to have little effect.) Argon was maintained at a pressureof 30 mTorr in the chamber while 200 nm of aluminum was sputterdeposited by the IMP process.

Thereafter, the wafer was transferred to a conventional PVD chamberwhere a layer of warm aluminum was deposited by traditional sputterdeposition. The layer of warm aluminum had a thickness of 1.5 μm asmeasured on a planar surface, and it was deposited with the substrateheld at a temperature of about 375° C.

The resulting structure was sectioned and examined with a scanningelectron microscope (SEM). The micrograph is shown in FIG. 5. In allcases, the warm aluminum completely filled the contact holes with novoids. The vertical feature seen in the top center and the tentstructure seen at the bottom of the contact holes are artifacts of theSEM.

Comparative Example

A comparative test was performed with the general structure suggested byXu et al. That is, the IMP aluminum layer of the invention was replacedby a warm standard PVD aluminum layer deposited at near to roomtemperature in a low-density plasma. Also, the pedestal was RF biased tocreate a DC self bias of −50V.

The resulting micrograph is shown in FIG. 6. In all cases, significantvoids have developed at the bottom of the contact holes, in one of thefour contacts extending half way up the hole. The voids indicate thatthere was insufficient reflow with the warn aluminum. Such voids areunacceptable in a commercial process because of the high contactresistance they produce. These experimental results should not beinterpreted to mean that the process of Xu et al. cannot be optimizedfor the structure and composition of the two examples, but the resultsdo show that, for at least one combination, the IMP aluminum layerprovides a better seed layer than the conventional PVD cold aluminumlayer.

The invention is preferably practiced on an integrated multi-chambertool, such as the Endura® 5500 platform illustrated in plan view in FIG.7, which is functionally described by Tepman et al. in U.S. Pat. No.5,186,718.

Wafers are loaded into the system by two independently operated loadlockchambers 100, 102 configured to transfer wafers into and out of thesystem from wafer cassettes loaded into the respective loadlockchambers. The pressure of a first wafer transfer chamber 104 to whichthe loadlocks can be selectively connected via unillustrated slit valvescan be regulated between the atmospheric or somewhat lower pressure ofthe cassette to a moderately low pressure, for example, in the range of10⁻³ to 10⁻⁴ Torr. After pump down of the first transfer chamber 104 andof the selected loadlock chamber 100, 102, a first robot 106 located inthe first transfer chamber 104 transfers the wafer from the cassette toone of two wafer orienters 108, 110 and then to a degassing orientingchamber 112. The first robot 106 then passes the wafer into anintermediately placed plasma preclean chamber 114, from whence a secondrobot 116 transfers it to a second transfer chamber 118, which is keptat a significantly lower pressure, preferably below 10⁻⁷ Torr andtypical 2×10⁻⁸ Torr. The second robot 116 selectively transfers wafersto and from reaction chambers arranged around its periphery.

A first IMP PVD chamber 120 is dedicated to the deposition of theTi-based barrier tri-layer. A second IMP PVD chamber 122 is dedicated tothe deposition of the IMP aluminum layer. Two standard PVD chambers 124,126 are dedicated to the deposition of the warm aluminum in alow-density plasma. It may be desirable to modify this configuration tohave two IMP PVD chambers for titanium deposition and only one standardPVD chamber for the warm aluminum. Each of the chambers 120, 122, 124,126 are selectively opened to the second transfer chamber 118 byunillustrated slit valves.

After the low-pressure PVD processing, the second robot 116 transfersthe wafer to an intermediately placed cool-down chamber 128, from whencethe first robot 106 withdraws the wafer and transfers it to a standardPVD chamber 130. This chamber deposits on the wafer a TiN layer ofcontrolled thickness and dielectric constant, which serves as ananti-reflection coating (ARC) over the metal layers just deposited inthe PVD chambers positioned around the second transfer chamber 118. TheARC layer facilitates photolithography of the highly reflective metallayers. After ARC deposition, the wafer is transferred to a cassette inone of the two loadlocks 100, 102. Of course, other configurations ofthe platform are possible with which the invention can be practiced.

The entire system is controlled by a controller 132 operating over acontrol bus 134 to be in communication with sub-controllers 136, asillustrated in FIG. 2, associated with each of the chambers. Processrecipes are read into the controller 132 by recordable media 137, suchas magnetic floppy disks or CD-ROMs, insertable into the controller 132,or over a communication link 138.

Many variations of the invention are possible, some of which arepresented below.

Hole filling may be applied to other applications than contact holes,for example, trenches, wall structures for dynamic memories, orinter-layer vias. If the underlying material is a metal, the barrierlayer can be simplified, perhaps with the elimination of either one orboth of the Ti layer and the graded TiN_(x) layer.

It is possible to deposit both of the aluminum layers in a single PVDreactor with the power supplies being changed between the twodepositions to emphasize respectively a directional and conformal IMPdeposition and a fast standard PVD deposition. It is also possible toachieve the IMP high-density plasma by means other than inductivecoupling, e.g, electron cyclotron resonance, helicon couplers, or remotemicrowave plasma sources.

It is possible to deposit the filling aluminum layer in an IMP processeven though this will require more time.

Since in the preferred arrangement of FIG. 7, the aluminum deposition isperformed in two separate chambers, the composition of the aluminumtarget and hence of the resultant film may be advantageously varied.That is, it is well known to alloy aluminum with various alloyingelements such as silicon and copper, and these alloying percentages mayvary between the targets of the two chambers to obtain particularlyadvantageous metal layers.

Although the invention has been described in regard to preferredmetallization of aluminum, it may be applied as well to other metalssuch as copper applied over the barrier layers. Of course, theafter-deposited layer should have a substantially non-refractivecomposition so as to differ from the underlying barrier tri-layer basedon titanium or other similar refractory metals, such as tantalum,cobalt, tungsten, and nickel.

Although the tri-layer structure is preferred, especially for siliconcontacts, in some situations such as vias to inter-layer metal layers,it may not be necessary to include the titanium siliciding layer or theTiNx graded layer. Barrier layers of other compounds of refractorymetals may be used with the invention.

The invention thus provides a way to assure that narrow inter-level holeare effectively filled with aluminum or other metals.

What is claimed is:
 1. An integrated processing tool, comprising: acentral transfer chamber including a robot for transferring wafers intoand out of said central transfer chamber from a higher-pressure chamber;a first physical vapor deposition chamber directly accessible via avalve with said central transfer chamber, having a target comprisingtitaniun, and achieving a high-density plasma; a second physical vapordeposition chamber directly accessible via a valve with said centraltransfer chamber, having a target comprising aluminum, and achieving ahigh-density plasma; and a third physical vapor deposition chamberdirectly accessible via a valve with said central transfer chamber,having a target comprising aluminum, and not achieving a high-densityplasma.
 2. The integrated processing tool of claim 1, wherein said firstand second physical vapor deposition chambers include inductive coilsfor coupling RF energy into respective ones of said deposition chambersand said third physical deposition chamber lacks an operative inductivecoil for coupling RF energy into said third physical deposition chamber.3. The integrated processing tool of claim 1, wherein said high-densityplasma is a plasma substantially filling an entire volume it is in andhaving an average ion density of greater than 10¹¹ cm⁻³ in a principalportion of said high-density plasma.
 4. The integrated processing toolof claim 1, wherein said central transfer chamber is maintainable at apressure of less than 10⁻⁷ Torr.
 5. An integrated processing tool,comprising: a central transfer chamber including a robot fortransferring wafers into and out of said central transfer chamber from ahigher-pressure chamber; a first physical vapor deposition chamber (a)directly accessible via a valve with said central transfer chamber, (b)having a target comprising a barrier metal, and a selectivelyactivatable valve connectable to a source of nitrogen, and (c) achievinga high-density plasma; a second physical vapor deposition chamberdirectly accessible via a valve with said central transfer chamber,having a target comprising a conductive metal, and achieving ahigh-density plasma; and a third physical vapor deposition chamberdirectly accessible via a valve with said central transfer chamber,having a target comprising said conductive metal, and not achieving ahigh-density plasma.
 6. The integrated processing tool of claim 5,wherein said barrier metal comprises titanium and said conductive metalcomprises aluminum.
 7. The integrated processing tool of claim 5,wherein said conductive metal comprises copper.
 8. The integratedprocessing tool of claim 5, wherein said barrier metal comprises arefractory metal selected from the group consisting of tantalum, cobalt,tungsten, and nickel.
 9. The integrated processing tool of claim 8,wherein said barrier metal comprises tantalum.
 10. The integratedprocessing tool of claim 5, wherein said first and second physical vapordeposition chambers include inductive coils for coupling RF energy intorespective ones of said deposition chambers and said third physicaldeposition chamber lacks an operative inductive coil for coupling RFenergy into said third physical deposition chamber.
 11. The integratedprocessing tool of claim 5, wherein said high-density plasma is a plasmasubstantially filling an entire volume it is in and having an averageion density of greater than 10¹¹ cm⁻³ in a principal portion of saidhigh-density plasma.
 12. The integrated processing tool of claim 5,wherein said central transfer chamber is maintainable at a pressure ofless than 10⁻⁷ Torr.
 13. An integrated processing tool, comprising: acentral transfer chamber including a robot for transferring wafers intoand out of said central transfer chamber from a higher-pressure chamber;a first physical vapor deposition chamber directly accessible via avalve with said central transfer chamber, having a target comprisingtitanium, and achieving a high-density plasma; a second physical vapordeposition chamber directly accessible via a valve with said centraltransfer chamber, having a target comprising aluminum, and achieving ahigh-density plasma; and a third physical vapor deposition chamberdirectly accessible via a valve with said central transfer chamberhaving a target comprising aluminum, and not achieving a high-densityplasma.
 14. The integrated processing tool of claim 13, wherein saidfirst and second physical vapor deposition chambers include inductivecoils for coupling RF energy into respective ones of said depositionchambers and said third physical deposition chamber lacks an operativeinductive coil for coupling RF energy into said third physicaldeposition chamber.
 15. The integrated processing tool of claim 13,wherein said high-density plasma is a plasma substantially filling anentire volume it is in and having an average ion density of greater than10¹¹ cm⁻³ in a principal portion of said high-density plasma.
 16. Anintegrated processing tool, comprising: a central transfer chamberincluding a robot for transferring wafers into and out of said centraltransfer chamber from a higher-pressure chamber; power supply means; afirst physical vapor deposition chamber (a) directly accessible via avalve with said central transfer chamber, (b) having a target comprisinga barrier metal, and a selectively activatable valve connectable to asource of nitrogen, (c) allowing said power supply means to excite afirst plasma in said first physical vapor deposition chamber, and (d) inconjunction with said power supply means being capable of producing saidfirst plasma as a high-density first plasma; a second physical vapordeposition chamber (a) directly accessible via a valve with said centraltransfer chamber, (b) having a target comprising a conductive metal, (c)allowing said power supply means to excite a second plasma in saidsecond physical vapor deposition chamber, and (d) in conjunction withsaid power supply means being capable of producing said second plasma asa high-density second plasma; and a third physical vapor depositionchamber (a) directly accessible via a valve with said central transferchamber, (b) having a target comprising said conductive metal, (c)allowing said power supply means to excite a third plasma in said thirdphysical vapor deposition chamber, and (d) in conjunction with saidpower supply means not being capable of producing said third plasma as ahigh-density third plasma.
 17. The integrated processing tool of claim16, wherein said barrier metal comprises titanium and said conductivemetal comprises aluminum.
 18. The integrated processing tool of claim16, wherein said conductive metal comprises copper.
 19. The integratedprocessing tool of claim 16, wherein said barrier metal comprises arefractory metal selected from the group consisting of tantalum, cobalt,tungsten, and nickel.
 20. The integrated processing tool of claim 19,wherein said barrier metal comprises tantalum.
 21. The integratedprocessing tool of claim 16, wherein said first and second physicalvapor deposition chambers include inductive coils for coupling RF energyfrom said power supply means respectively into respective ones of saiddeposition chambers and said third physical deposition chamber lacks anoperative inductive coil for coupling RF energy into said third physicaldeposition chamber.
 22. The integrated processing tool of claim 16,wherein said high-density plasma is a plasma substantially filling anentire volume it is in and having an average ion density of greater than10¹¹ cm⁻³ in a principal portion of said high-density plasma.